When there is a failure in an electric vehicle or the electric vehicle is deenergized normally, a relay in a high-voltage system of the electric vehicle is required to be turned off so as to open a voltage circuit of a power battery in the electric vehicle.
In a related art, in a normal opening process of the high-voltage system circuit, opening the high-voltage system circuit may be implemented by turning oft for example, the positive relay and the negative relay. For example, an instruction of turning off the positive relay (such as a positive contactor (PC)) may be sent to turn off the positive relay, and an instruction of turning off the negative relay (such as a negative contactor (NC)) may be sent to turn off the negative relay, such that the high-voltage system circuit may be opened. When an urgent failure (such as an insulation failure, an over-voltage fault of the power battery group, an over-temperature fault of the power battery group, an over-current fault of the power battery group, etc.) occurs, the circuit may be opened urgently by turning off components, such as, the positive relay, the negative relay, or a pre-charging relay (such as a pre-charging contactor (PreC)). The control method of turning off the relay urgently is simple. For example, an instruction of turning off the positive relay, an instruction of turning off the negative relay and an instruction of turning off the pre-charging relay may be sent to the high-voltage system simultaneously so as to turn off the positive relay, the negative relay and the pre-charging relay, such that a user's safety may be guaranteed. However, since a loop current of the voltage circuit of the power battery is relatively larger, one or more of these relays cannot be turned off normally, thus bringing a hidden danger. In addition, it is unable to determine whether a relay is really in a turned-off state. If a relay that needs to be turned off is not turned oft an opportunity of correcting this error may be lost. As such, the security of the electric vehicle cannot be guaranteed, and significant negative consequences may be caused.